Replacing The Open And Close Pilot Valves; Evacuating The Mechanism - ABB Mechanism HMB-8 Instructions Manual

5. Remove the four cap screws 51115 from the cover
51023 and pull the cover straight out from the main
body casting. You may encounter some resistance
from the O-ring 51078 on the cover. (The eccentric
shaft 51015 and inner ring 51021 will also come off
with the cover 51023.)
6. Remove the pump element 51014 by pulling the ele-
ment straight out of the casting. You may encounter
some resistance from the O-ring on the check valve.
7. Replace the pump element 51014 with a new pump
element. Be sure the pump element is seated securely.
Caution
Be certain that the pump element is properly
positioned.
8. Re-install the cover 51023. Use a new O-Ring.
9. Apply Loctite 242 to the cap screws 51115 and re-
install the screws.
10. Refer to section 4.3.7 to re-install the pump motor and
sections 4.3.5 and 4.3.6.2 to evacuate and refill the
mechanism with hydraulic oil.
4.3.4

Replacing the Open and Close Pilot Valves

To replace the open pilot valve(s) 51005 (Figs. 1 and 8) and
close pilot valve 51004:
1. Remove the mechanism cover 51028.
2. Be sure that the mechanism is in the OPEN position
and the pressure inside the mechanism is equalized
as described in section 4.1.1.
3. Drain the hydraulic oil from the mechanism by per-
forming the procedure described in section 4.3.2.
4. Remove the two screws holding the plug-type wiring
connector to the pilot valve; remove the connector.
5. Remove the pilot valve (to be replaced) by unfastening
the four socket head bolts holding it in place.
Important: Clean and remove all remaining oil from the
sealing surface, then make sure the pilot
valve is in the correct position.
6. Replace the old pilot valve with a new pilot valve.
7. Refer to sections 4.3.5 and 4.3.6 to evacuate and refill
the mechanism with hydraulic oil.
4.3.5

Evacuating the Mechanism

Any time hydraulic oil has been drained or any procedure
has been performed which could introduce air into the oil,
the air within the mechanism body must be evacuated. A
vacuum should be applied to the mechanism body before
refilling the mechanism with hydraulic oil.
If unusual breaker timing operations occur after this proce-
dure is performed, it may be necessary to repeat the
procedure. This procedure is recommended after trans-
portation, especially for mechansisms not shipped on a
circuit breaker.
HMB-8 / HMB-8.7 Mechanism
Important: After any maintenance that could allow even
small amounts of air to enter the hydraulic sys-
tem, evacuate the air and refill the system with oil.
Slow opening or closing times during mecha-
nism timing tests or excessive or erratic pump
up time of the hydraulic system may indicate the
presence of air in the hydraulic system. The air
needs to be evacuated using this procedure.
Remove the breaker from service; isolate it and ground it
before proceeding.
To evacuate the mechanism:
1. Remove the mechanism cover 51028 (Fig.1).
2. Be sure that the mechanism is in the OPEN position
and the pressure inside the mechanism is equalized
as described in section 4.1.1.
3. Remove the cap from the oil fill port 51127. Be sure that
the oil drain valve 51013 is closed.
4. Connect a small two-stage vacuum pump to the oil fill
port (a special Ermetto hydraulic pressure fitting will be
required). A minimum 3 foot vertical, transparent hose
is desirable to monitor the oil quantity pulled out of the
mechanism during the vacuum process.
5. Be sure that the pressure equalizing handle 51017
(Figure 2) is rotated out to open the pressure relief valve.
6. Apply a vacuum to remove air from the mechanism
body. Pull a 1.5 psia vacuum (10 kPa, 100 millibar, 3
mm of mercury) for about 5 minutes. Take care to not
pull oil into the vacuum pump. A lesser initial vacuum
can be used to limit the amount of oil pulled out until
most of the air is removed from the mechanism.
While the vacuum is being applied, push in on the
armature of the close and open pilot valves 51004 (Fig.
8) and 51005 for several seconds each.
Rotate the large bevel gear 51019 (Fig. 5) of the pump
several times.
Important: If significant hydraulic oil is in the mechanism
while performing the evacuation procedure,
insert an in-line valve between the vacuum
pump and the mechanism. Throttle this valve
to initially apply the vacuum very slowly to
prevent the oil from foaming and being sucked
into the vacuum pump.
7. Draw a higher vacuum of .15 to .22 psia (1 to 1.5 kPa,
10 to 15 millibar, or.3 to .45 mm of mercury) for about
5 minutes.
While the vacuum is being applied, push in on the
armature of the close and open pilot valves 51004 (Fig.
8) and 51005 for several seconds each.
Rotate the large bevel gear 51019 (Fig. 5) of the pump
several times.
8. Proceed to section 4.3.6.2 to refill the mechanism with
hydraulic oil if it had been drained prior to applying the
vacuum.
641P026-008
(formerly HMB-11)
©
Page 11
4 November 2005